Method of calculating high-resolution 3D wind numerical information considering detailed topographic information
Provided is a method of calculating high-resolution three-dimensional wind numerical information considering detailed topographic information, the method performing, when the wind numerical data of the operational LDAPS model is calculated (S 100 ), a downscaling process based on the detailed topographic information using the wind numerical data as an input data, wherein the downscaling process performs a preprocessing process of converting a coordinate system and interpolating horizontal and vertical numerical data (S 200 ), performs a process of adjusting roughness lengths (S 300 ), correcting heights (S 400 ), and correcting a subgrid-scale terrain drag effect (S 500 ) on the basis of the detailed topographic information, and finally generating data that has gone through each of the processes as high-resolution wind numerical data (S 600 ).
1 . A method of calculating high-resolution three-dimensional wind numerical information considering detailed topographic information, the method performing, when wind numerical data of an operational (Local Data Assimilation Prediction System) LDAPS model is calculated (S 100 ), a downscaling process based on the detailed topographic information using the wind numerical data as an input data, wherein
the downscaling process
performs a preprocessing process of converting a coordinate system and interpolating horizontal and vertical numerical data (S 200 ),
performs a process of adjusting roughness length (S 300 ), correcting height (S 400 ), and correcting a subgrid-scale terrain drag effect (S 500 ) on the basis of the detailed topographic information, and
finally generates data that has gone through each of the processes as high-resolution wind numerical data (S 600 ),
wherein step S 500 is a method of correcting vertical wind numerical data, wherein
the procedure is configured of calculating a subgrid-scale topographic roughness length, estimating attenuation of momentum using logarithmic wind distribution, and correcting the estimated attenuation of momentum, and
the sub-grid scale topographic roughness length is calculated considering high-resolution topographic height numerical data on the basis of a low-resolution grid size, and
the subgrid-scale topographic roughness length applies a roughness length relational formula calculated using a large eddy simulation model under ideal surface roughness conditions, and is defined as shown in Equation (e)
z 0,SSO =ασ h (1+ S k ) β Equation (e), wherein
σ h and S k denote standard deviation and skewness of a sub-grid scale topographic height, respectively, and α and β are constants obtained through a large eddy simulation, and
wherein at step S 500 , the attenuation of momentum generated due to sub-grid scale topographic roughness is estimated by applying logarithmic wind speed distribution applied in the vegetation roughness correction, and is defined as shown in Equation (f)
f
D
(
z
)
=
Δ
u
_
(
z
)
u
_
(
z
)
=
ln
(
h
ABL
/
z
0
)
ln
(
z
/
z
0
,
local
)
ln
(
h
ABL
/
z
0
,
local
)
ln
(
z
/
z
0
)
,
Equation
(
f
)
wherein
f D (z) denotes a momentum attenuation rate at each height, ū(z) means wind data at vertical height z at which vegetation roughness correction is performed, Δū(z) denotes a difference of logarithmic wind data applying vegetation roughness length and sub-grid scale topographic roughness, z 0,local is calculated by the sum of the vegetation roughness length and the sub-grid scale topographic roughness, and means ground surface roughness of the wind data correction point, and h ABL means height of the atmospheric boundary layer, and is set as 3.5 h ref to reflect local topographic characteristics,
the method further comprising performing weather prediction based on a predicted wind speed using the high-resolution wind numerical data (S 600 ).
2 . The method according to claim 1 , wherein at step S 100 , the wind numerical data is defined as U wind and V wind expressed in the form of a two-dimensional vector, and is constructed using FORTRAN and Korn-shell languages based on an x86 Linux server.
3 . The method according to claim 2 , wherein input of the wind numerical data of the operational LDAPS model at step S 100 is targeting numerical data of 1.5 km grid size generated in a pp format, and an execution process is largely configured of recognition of files produced according to prediction time of corresponding data, and input of related files.
4 . The method according to claim 3 , wherein interpolation is performed horizontally and vertically at step S 200 after the coordinate system of the U wind and V wind fields of the operational LDAPS model is converted into an Arakawa-B grid,
the horizontal interpolation process applies a distance-weighted bi-linear interpolation using a 2×2 operational LDAPS model including a target point, and
the vertical interpolation process performs interpolation by applying a distance weight in the vertical direction in the same way as the horizontal interpolation.
5 . The method according to claim 4 , wherein at step S 300 , wind data is corrected by applying a vegetation roughness length calculated based on the detailed topographic information, and correction of the vegetation roughness length is performed through a formula as shown in Equation (a)
u
RA
(
z
)
=
u
*
k
ln
(
z
z
0
)
=
u
(
h
RA
)
ln
(
z
/
z
0
)
ln
(
h
RA
/
z
0
)
,
Equation
(
a
)
wherein
u RA (z) means wind data that has gone through roughness adjustment at vertical height z, u* is friction velocity, k is von Karman constant (0.4), z is a height at which wind correction is performed, Z 0 means a vegetation roughness length at a corresponding point, u(h RA ) denotes wind data of input data (operational LDAPS model), and h RA is a reference height for roughness adjustment, which means an upper end of vertical logarithmic distribution of wind.
6 . The method according to claim 5 , wherein step S 400 is a process of correcting changes in wind generated due to a difference between the height of a model that generates the wind field and the actual height, and is performed on the basis of a linear theory assuming a neutral atmosphere on a terrain calculated at a high resolution, and the process is defined as shown in equation (b)
Δ u HC ( z )= u ( h HC ) e −KZ ΔH Equation (b), wherein
Δu HC (z) means corrected wind data at vertical height z, u(h HC ) means wind of input data (operational LDAPS model) at a reference height h HC for height correction, k is a topographic wave number, and ΔH HC denotes height difference between high-resolution topographic data and low-resolution topographic data at the same target point.
7 . The method according to claim 6 , wherein at step S 400 , the reference height h HC for height correction and the topographic wave number k input into equation (b) are defined as shown in equations (c) and (d), respectively,
h
HC
=
1
k
Equation
(
c
)
k
=
π
A
/
S
H
/
2
,
Equation
(
d
)
wherein
H/2 and A/S mean topographic peak height and topographic silhouette roughness length calculated from the high-resolution topographic data.
8 . The method according to claim 1 , wherein at step S 500 , vertical wind distribution ū SSO (z) applied with the sub-grid scale terrain drag effect is calculated as shown in equation (g)
ū SSO ( z )= ū ( z )(1− f D ( z )) Equation (g).
9 . The method according to claim 8 , wherein at step S 600 , the high-resolution wind numerical data is generated to be divided into Netcdf4 format files in a set directory for each prediction time, and variables generated in each file include U wind, V wind, and wind speed.